In an industrial apparatus, feedback control is used to realize necessary operation. In the feedback control, adjustment of a control gain used to calculate an operation amount from a detected control amount is necessary.
As one of methods for appropriately adjusting the control gain, there is a limit cycle method. The limit cycle method is a method of, by performing control for selecting one from two operation amounts and outputting the operation amount called binary control, vibrating a control amount at a constant cycle or a cycle regarded as constant, identifying dynamic characteristics of a control target on the basis of a vibration waveform, and calculating a control gain (Non Patent Literature 1). The vibration waveform is called limit cycle waveform.
In the limit cycle method, to identify the dynamic characteristics of the control target, it is necessary to select one of the operation amounts of the binary control on the basis of a plus or minus sign of a control deviation, vibrate the control amount at the constant cycle or the cycle regarded as constant, and generate the limit cycle waveform. However, in the limit cycle method, when noise is included in the detected control amount and the plus or minus sign of the control deviation is reversed because of the influence of the noise, on/off control operates irrespective of the dynamic characteristics of the control target. In some case, chattering occurs, the limit cycle waveform of the constant cycle or the cycle regarded as constant cannot be obtained, and the dynamic characteristics of the control target cannot be identified.
Patent Literature 1 mentions that, even when noise is included in the detected control amount, the limit cycle waveform of the constant cycle or the cycle regarded as constant is generated. Patent Literature 1 mentions that the chattering of the binary control due to the influence of the noise included in the detected control amount is prevented by providing a hysteresis characteristic in the determination of the plus or minus sign of the control deviation. Patent Literature 1 mentions that the dynamic characteristics of the control target is identified and the control gain is calculated even when noise is included in the detected control amount.